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Early word learning 1 Early word learning and conceptual development:
Everything had a name, and each name gave birth to a new thought.1
Sandra R. Waxman & Erin M. Leddon
Northwestern University
Synopsis
Perhaps more than any other developmental achievement, word-learning stands at the very
intersection of language and cognition. Early word-learning represents infants’ entrance into a truly
symbolic system and brings with it a means to establish reference. To succeed, infants must identify
the relevant linguistic units, identify their corresponding concepts, and establish a mapping between
the two. But how do infants begin to map words to concepts, and thus establish their meaning? How
do they discover that different types of words (e.g., “dog” (noun), “fluffy” (adjective), “begging”
(verb) refer to different aspects of the same scene (e.g, a standard poodle, seated on its hind legs and
holding its front paws in the air)? We have proposed that infants begin the task of word-learning with
a broad, universal expectation linking novel words to a broad range of commonalities, and that this
initial expectation is subsequently fine-tuned on the basis of their experience with the objects and
events they encounter and the native language under acquisition. In this chapter, we examine this
proposal, in light of recent evidence with infants and young children.
Introduction
Infants across the world’s communities are exposed to vastly different experiences. Consider,
for example, one infant being raised in a remote region of the Guatemalan rainforest, another growing
up in the mountains of rural Switzerland, and a third being raised in Brooklyn, NY. Each infant will
live in a world that is unimaginable to the other, surrounded by objects and events that are foreign to
the other, and immersed in a language that the other cannot begin to understand. Yet despite these vast
Early word learning 2 differences in experience, infants across the world display striking similarities in the most fundamental
aspects of their conceptual and language development.
Within the first year of life, each of these infants will begin to establish systematic links
between words and the concepts to which they refer. On the conceptual side, they will begin to form
categories of objects that capture both the similarities and differences among the objects they
encounter. Most of these early object categories will be at the basic level (i.e., dog) and the more
inclusive global level (i.e., animal). Infants will begin to use these early object categories as an
inductive base to support inferences about new objects that they encounter. They will also begin to
relate categories to one another, implicitly, on the basis of taxonomic (e.g., dogs are a kind of animal),
thematic (e.g., dogs chase tennis balls), functional (e.g., dogs can pull children on sleds) and other
relations. Infants’ early object and event categories will provide a core of conceptual continuity from
infancy through adulthood.
Concurrent with these conceptual advances, infants in each community will make remarkably
rapid strides in language acquisition. Even before they begin to understand the words of their native
language, infants show a special interest in the sounds of language. Newborns respond to the emotional
tone carried by the melody of human speech (Fernald, 1992a, b), and prefer speech sounds to other
forms of auditory input (Jusczyk & Kemler Nelson, 1996; Vouloumanos & Werker, 2004, 2007).
Within the first six months, infants become perceptually attuned to the distinct prosodic, morphologic,
and phonologic elements that characterize their native language (Jusczyk & Kemler Nelson, 1996;
Kemler Nelson, Hirsh-Pasek, Jusczyk, & Cassidy, 1989; Morgan & Demuth, 1996; Shi, Werker, &
Morgan, 1999; Werker, Lloyd, Pegg, & Polka, 1996; see Saffran, Werker, & Werner, 2006 for a
review). By their first birthdays, infants begin to produce their first words. These early words tend to
refer to salient individual objects (e.g., “Mama”), categories of objects (e.g., “cup”, “doggie”), social
routines (e.g., “bye-bye”), and actions (e.g., “up”). Across languages, infants’ earliest lexicons tend to
show a “noun advantage”, with nouns referring to basic-level object categories (e.g., cup, dog) being
Early word learning 3 the predominant form (see Bornstein, Cote, Maital, Painter, Park, & Pascual, 2004 for an excellent
cross-linguistic developmental review). By their second birthdays, most infants have mastered
hundreds of words of various grammatical forms (e.g., nouns, verbs, adjectives) and have begun to
combine these into short, well-formed phrases that conform broadly to the syntactic properties of their
native language.
This brief sketch illustrates several early milestones along the road of language and conceptual
development. Infants naturally form categories to capture commonalities among objects and events and
learn words to express them. What is perhaps even more intriguing is that these two advances do not
proceed independently. Instead, there are powerful implicit links between them.
Links between early language and conceptual development: A view through the lens of word-
learning
The links between early language and conceptual development are most clearly viewed through
the lens of early word-learning. Word learning supports infants’ subsequent discovery of the
fundamental syntactic properties of the native language (See Gillette, Gleitman, Gleitman, & Lederer,
1999; Snedeker & Gleitman, 1999; Pinker, 1984, 1989; Waxman, 1999a; Waxman, 1999b) as well as
the evolution of increasingly abstract conceptual representations. Moreover, from the onset of
acquisition, the process of word-learning involves powerful, implicit links between the linguistic and
conceptual systems. Even before infants begin to speak, novel words guide their attention to objects,
and highlight commonalities and differences among them (Balaban & Waxman, 1997; Booth &
Waxman, 2002; Fulkerson & Haaf, 2003, 2006; Fulkerson & Waxman, 2007; Graham, Kilbreath, &
Welder, 2004; Keates & Graham, 2008; Waxman & Markow, 1995; Welder & Graham, 2006; Xu,
1999). But these links are not as precise as those held by older children and adults. How does their
development proceed?
We have proposed that 1) infants across the world’s language communities begin the task of
word learning equipped with an initially general and universal expectation, and 2) this early
Early word learning 4 expectation is then shaped by the structure of the particular language under acquisition. In our most
recent work, which will be reviewed here, we have sought to uncover the origin and unfolding of these
links (Booth & Waxman, 2003; Waxman & Booth, in press; Fulkerson & Waxman, 2007; Klibanoff &
Waxman, 2000; Waxman, 1998; Waxman & Booth, 2000a; Waxman & Booth, 2001b; Waxman, Lidz,
Braun, & Lavin, in press; Waxman & Markow, 1995). To amplify this topic, we will discuss what it
takes to learn a word, to establish a mapping between the linguistic entities that we call words and the
corresponding entities and events in the world. We then go on to trace the origin and emergence of
these links in infants.
What does it take to learn a word?
Perhaps the most celebrated example of word-learning comes from Helen Keller’s
autobiography. As Keller recounts, “...my teacher placed my hand under the spout. As the cool stream
gushed over one hand she spelled into the other the word water, first slowly, then rapidly. I stood still,
my whole attention fixed upon the motions of her fingers. Suddenly I felt a misty consciousness as of
something forgotten – a thrill of returning thought; and somehow the mystery of language was
revealed to me. I knew then that ‘w-a-t-e-r’ meant the wonderful cool something that was flowing
over my hand. That living word awakened my soul, gave it light, hope, joy, and set it free! ... I left the
well-house eager to learn. Everything had a name, and each name gave birth to a new thought.”
(Keller, 1904 p. 22-23)
This memorable passage poignantly conveys the obstacles in first establishing a
correspondence between the abstract entities that we call words and their referents in the world. It also
conveys the power of such word-to-world mappings, once they are attained. But the scenario in this
passage differs in important ways from the more typical circumstances in which infants’ first words are
acquired. One important difference is the age of acquisition. Infants tend to produce their first words at
approximately one year of age. Keller, in contrast, learned water at approximately seven years of age.2
Early word learning 5 A second difference is the extent to which names are deliberately “taught”. Psycholinguists and
anthropologists have conducted detailed observations of naming practices across cultures. In some
cultures (c.f., Western, college-educated communities), caretakers do name objects deliberately for
their infants, even before the infants themselves can speak. Yet in many other communities, (c.f.,
Kahluli, see Ochs and Schieffelin, 1984), caretakers refrain from speaking directly to infants until the
infants themselves have begun to speak. Clearly, then, infants can discover the meaning of novel words
even in the absence of direct tutoring.
A third relevant difference is in the presentation of the new word. In the typical course of
events, words are seldom, if ever, presented in isolation, as Keller’s tutor presented the word w-a-t-e-r.
Instead, words tend to be embedded in a fluent stream of continuous speech (e.g., “Look at the water!
Oooh…it’s so cold. Isn’t that cold water?”), leaving it to the infant to parse the novel word. How do
they succeed in these cases? At a most general level, it helps that infants devote special attention to
human speech, for this puts them in a good position to begin to single out the novel words (Jusczyk &
Kemler Nelson, 1996). Moreover, in many cultures, caretakers use a special speech register
(sometimes known as infant-directed speech or ‘motherese’) when addressing infants and young
children. Two characteristic features of this speech register -- exaggerated pitch contours and phrase
boundaries – help infants to identify words and phrases in the continuous speech stream (Gleitman &
Wanner, 1988).
A fourth difference concerns the identification of the referent of the novel word. Unlike Keller,
infants must identify the referent of a novel word amidst an ever-changing current of events. In many
cases, the referent may be absent entirely (e.g., “Let’s call Daddy”, uttered as the caretaker picks up a
phone), or may make only a fleeting appearance (e.g., “Look at the monkey”, uttered as a monkey
makes a brief appearance in its habitat at the zoo). And even if the referent is present throughout the
naming episode, there is no guarantee that the infant will be attending to it at the time that the novel
Early word learning 6 word is introduced (e.g., “Go find your teddy-bear”, uttered as a caretaker tries (in vain) to pull the
infants’ attention away from the sleeping family cat).
The puzzle of word-learning
Thus, in the natural course of word-learning, an infant is faced with a difficult three-part
puzzle: (1) parsing the relevant word from the ongoing stream of speech, (2) identifying the relevant
entity in the ongoing stream of activity in the world, and (3) establishing a word-to-world
correspondence. To put matters more formally, successful word-learning rests on the infant’s ability to
discover the relevant linguistic units, the relevant conceptual units, and the mappings between them.
Notice also that each piece in the word-learning puzzle is itself dependent on infants’ ability to
recruit other perceptual and psychological capacities. Consider, for example, the ability to parse words.
We know that newborns prefer to listen to human speech—and particularly infant-directed speech —as
compared to other sources of auditory stimulation. However, the function of infant-directed speech
appears to change during the first year of life (Fernald, 1992b). Initially, infant-directed speech serves
primarily to engage and modulate the infant’s attention. Toward the end of the first year, “…words
begin to emerge from the melody” (Fernald, 1992a p. 403). By approximately 9 to 10 months, infants
become increasingly sensitive to the cues (morphologic, phonetic and prosodic cues) that mark word
and phrase boundaries (Jusczyk & Aslin, 1995; Kemler Nelson et al., 1989).
Infants’ growing sensitivity to these perceptual cues permit them to distinguish two very broad
classes of words: open class words (or, content words, including nouns, adjectives, verbs) and closed
class words (or, function words, including determiners and prepositions). Research using a preferential
listening task reveals that even 6-month-old infants prefer to listen to open class words (Gomez, 2002;
Shi & Werker, 2003). This preference is likely related to the fact that such words are perceptually more
salient: they receive greater stress and more interesting melodic contours than closed class words.
Since this preference exists well before infants begin to map words systematically to meaning, it is
reasonable to assume that it is perceptually based and independent of meaning. Yet this perceptually-
Early word learning 7 based preference represents an important step on the way to word-learning, for it insures that infants
attend to just those words (the open class, content words) that are required if they are to anchor their
first word-to-world mappings. (Jusczyk & Kemler Nelson, 1996; Morgan & Demuth, 1996; Werker et
al., 1996).
Early word-learning also draws upon the infants’ perceptual and conceptual ability to identify
objects and events in their environment, and to notice commonalities among them. During the first
year, infants demonstrate a great deal of core knowledge about objects (Baillargeon, 2000; Spelke,
2000). They also form a repertoire of pre-linguistic concepts, including category-based (e.g., dog,
bottle) and property-based (e.g., red, soft) commonalities. Since many of these concepts are formed
before the advent of word-learning, it is reasonable to assume that they are independent of language
and are universally available. Each object and concept is, in essence, a candidate for a word’s meaning.
The infants’ task is to discover which candidate meaning maps to the word that they have parsed.
The third piece of the word-learning puzzle—grasping the symbolic and referential power of
words—further requires infants to draw upon fundamental notions related to human behavior: inferring
the goals and intentions of others (Waxman & Gelman, in press). For example, the ability to establish a
mapping between a word and its referent is predicated upon infants’ capacity to infer that the speaker
intended to name the designated object. By the end of the first year of life, infants have begun to make
such connections (Ahktar & Tomasello, 2000); for example, they spontaneously follow a speaker’s
line of regard to identify the object to which an adult speaker is attending (Baldwin & Baird, 1999;
Guajardo & Woodward, 2000).
In addition to these three central elements, successful word-learning requires infants to go
beyond a word-to-object mapping. To use a word consistently over time, infants must be able to store
in memory the correspondence between a word and its intended referent. They must also be able to
generalize a newly learned word appropriately beyond the individual on which it was taught. For
example, to be able to apply the word dog to a new, and (as yet) unlabeled object, that child must make
Early word learning 8 an inference regarding its extension. Infants’ spontaneous extensions indicate that they do not merely
map words to the objects on which they were introduced. Infants go beyond word-to-object mappings
to establish word-to-category mappings (Gelman, 2006; Waxman & Lidz, 2006).
Different kinds of words highlight different aspects of a scene
To complicate matters further, many different words -- indeed many different types of words –
may be offered in a single naming episode. Importantly, each type of word highlights a different aspect
of the same observed scene and supports a unique pattern of extension. For example, in English, count
nouns (“Look, it’s a dog”) typically refer to the named object itself and are extended spontaneously to
other members of the same object kind (other dogs); proper nouns (“Look, it’s Zeus”) also refer to the
named individual, but these are not extended further. Adjectives can also be applied correctly to that
individual (“Look, it’s furry”); they refer to a property of the individual, and are extended to other
objects sharing that property. Verbs, in contrast, are used to describe the event, or the relation in which
the individual(s) are participating (“Look, it’s running”), and are extended to other relations of the
same type.
Considerable research has documented that by two-and-a-half to three years of age, children are
sensitive to many of these links between kinds of words and kinds of relations among objects, and
recruit these links in the process of word learning (For a review, see Waxman & Lidz, 2006). This
establishes that preschool-aged children have the linguistic capacity to distinguish among the relevant
syntactic forms (e.g., count noun vs. adjective) and the conceptual or perceptual ability to appreciate
many different kinds of relations among objects, and a tacit expectation that these linguistic and
conceptual abilities are interwoven.
The proposal: The acquisition of word-to world links
But how do infants acquire these specific word-to-world links? Which, if any, are available at
the very onset of lexical acquisition, and how are these shaped over the course of development? The
evidence discussed above suggests that infants begin with a perceptual preference for listening to open
Early word learning 9 class words, with a repertoire of accessible perceptual and conceptual categories, and with a broad
expectation that novel (open class) words, independent of their grammatical form, highlight
commonalities among named objects. This initial link serves (at least) three essential functions. First,
with words directing attention to commonalities, this link facilitates the formation of an expanding
repertoire of concepts, concepts that may not have been detected in the absence of a novel word.
Second, this initial expectation supports infants’ first efforts to establish symbolic reference, to form a
set of stable ‘word-to-world’ mappings. Finally, and perhaps most radically, this initial expectation sets
the stage for the evolution of the more specific expectations linking particular types of words (nouns,
adjectives, verbs) to particular types of relations among objects (object categories, object properties,
event categories) in the native language under acquisition (Waxman, 1999b).
How might this evolution come about? Infants’ early expectation (that words refer to
commonalities) supports the establishment of a rudimentary lexicon. This lexicon serves as a base
upon which infants a) begin to tease apart the various grammatical forms presented in the language
under acquisition, and b) begin to detect the correlations between these emerging forms and their
meanings. We argue that infants’ initial expectation (linking words in general) to commonalities (in
general) will direct their attention to just the sorts of regularities in the input that will promote the rapid
discovery of the distinct grammatical forms present in the language under acquisition, and will support
the induction of more specific expectations.
The evidence: The evolution of infants’ word-to world expectations
To test this proposal, we must identify the expectation(s) of infants on the threshold of word-
learning, and observe how these are shaped in the course of acquiring their native language. The
sections that follow describe the influence of language on categorization in infants and young children.
The focus is on how infants and young children begin to map words to meaning, and how their
expectations vary according to the word’s grammatical category, be it noun, adjective, or verb. We
Early word learning 10 examine the acquisition of words in each of these grammatical categories, considering evidence from a
variety of measures, including time-course analyses of children’s responses to a novel word. We
conclude with a discussion of new avenues for research on word learning.
Unifying features of the experiments
The experiments described in this section all share several important features. Each is
essentially a categorization task, tailored to suit the very different behavioral repertoires of infants vs.
young children. In each, the goal is to observe the influence of language on categorization. To do so,
we compare subjects’ performance in "neutral" conditions (involving no novel words), with their
performance when they are introduced to novel words. Because our goal is to examine an abstract
linkage between particular grammatical forms and particular types of relations, we introduce novel
words (e.g., blicket), rather than familiar (e.g., animal) words. This insures that the words themselves
carry no a priori meaning for the child. To examine the influence of grammatical form, we vary the
frame in which the novel word is embedded. We use short, simple syntactic constructions that 1) are
typical in infant- and child-directed speech, and that 2) provide unambiguous contextual evidence that
the novel word is either a count noun, an adjective, or a verb. In all conditions, these constructions are
presented to infants in a speech register known as “motherese” or infant-directed speech because
infants find it especially engaging. In the Novel Noun conditions, we introduce the novel word, saying,
for example, "This is a blicket." In the Novel Adjective and Novel Verb conditions, we present the
same word using a different frame, saying, for example, “This is a blick-ish one," or “She is blicking
the cup.” In the No Word control conditions, we engage the infants with infant-directed speech, bur
offer no novel word, simply saying, for example, "Do you like this?” or “Look at this". Performance
in this No Word control condition assesses how readily subjects form the various categories presented
in our tasks (e.g., dog, animal, purple, running). Performance in the Noun, Adjective and Verb
conditions assesses the role of naming in this important endeavor, and permit us to test the specificity
Early word learning 11 of the relation between form and meaning. Because nouns, adjectives, and verbs alike can be used to
describe different aspects of the very same scene, this is an important control.
Naming and categorization
Prelinguistic infants: Cognitive consequences of naming. Recent research suggests that naming
has several cognitive consequences, even for infants who have not yet begun to produce words on their
own. For example, by 10 months, infants devote more attention to objects that have been named than
to objects that have been presented in silence (Baldwin & Markman, 1989). This raises two further
questions: First, does the increased attention stem from the general attention-engaging functions of
auditory stimuli, or does it reflect something special about words? Second, does naming promote
attention to a named individual only, or does it exert an influence beyond the named individual?
Several recent studies have compared the effect of novel words versus tone sequences on
infants’ categorization behavior, and these suggest that words are indeed special (Balaban & Waxman,
1997; Fulkerson & Haaf, 2003, 2006; Fulkerson & Waxman, 2007). In one study, Fulkerson and
Waxman (2007) assessed 6-month-old infants’ performance when presented with words versus tones
in a novelty-preference task. During a familiarization phase, infants saw a sequence of colorful slides,
each depicting a different member of a basic-level category (e.g., dinosaurs). To examine the influence
of words, they randomly assigned infants to either a Word or a Tone condition. For infants in the Word
condition, a naming phrase (e.g., “Oh look, it’s a toma! Do you see the toma?”) accompanied the
familiarization trials. For infants in the Tone condition, a sine-wave tone (matched to the naming
phrase in amplitude, duration, and pause length) accompanied the familiarization trials. Next, infants
were presented with a test trial, including a) a new member of the now-familiar category (e.g., another
dinosaur) and b) an object from a novel category (e.g., a fish). Test trials were presented in silence.
The authors reasoned that if words focus attention on commonalities among objects, then
infants hearing words during familiarization should notice the commonalities among the
familiarization objects. In that case, the infants should reveal a preference for the novel test object
Early word learning 12 (e.g., the fish). If this effect is specific to words, and not to auditory stimulation more generally, then
infants hearing tones during familiarization should be less likely to notice these commonalities and less
likely to reveal a novelty preference at test. This is precisely the pattern of results obtained. We can
therefore conclude that for infants as young as 6 months of age, there is indeed something special
about words, and that providing a shared name for distinct individuals highlights commonalities among
them.
In addition to supporting object categories, naming supports the process of object individuation.
Evidence suggests that 10-month-olds find it difficult to keep track of the unique identities of two
distinct objects (e.g., a ball and a duck), especially if these objects are presented in constant motion,
with one appearing and disappearing from one side of a screen, and the other appearing and
disappearing from the other side of the same screen (Xu & Carey, 1996). However, infants’ difficulty
tracking these distinct objects diminishes dramatically if each is labeled with a distinct name as it
emerges from behind the screen.
Together, these results reveal that naming has powerful cognitive consequences, even in pre-
linguistic infants. Naming supports the establishment of a repertoire of object categories and provides
infants with a means of tracing the identity of individuals within these categories throughout
development. These links appear before the advent of productive language.
Infants on the threshold of word learning: Changing expectations of word-to-world mappings.
In the previous section, we established that words have a unique influence on prelinguistic infants’
construals of individual objects and object categories. In this section, we trace the evolution of infants’
expectations regarding word-to-world mappings as they cross the important developmental threshold
of producing words on their own. At this developmental point, how do words influence infants’
attention to individual objects and object categories?
Words as invitations to form categories. One series of experiments examined the influence of
novel words on object categorization in 12- to 14-month old infants (see Waxman & Markow, 1995 for
Early word learning 13 a complete description). We used a novelty-preference task (See Figure 1 for a sample set of stimuli
and introductory phrases). During a familiarization phase, an experimenter offered an infant four
different toys from a given category (e.g., four animals) one at a time, in random order. This was
immediately followed by a test phase, in which the experimenter simultaneously presented both a) a
new member of the now-familiar category (e.g., another animal) and b) an object from a novel
category (e.g., a fruit). Each infant completed this task with four different sets of objects. Two
involved basic level categories (e.g., horses vs. cats); two involved more abstract superordinate level
categories (e.g., animals vs. fruit). Infants manipulated the toys freely. Their manipulation served as
the dependent measure.
To test the influence of novel words, we randomly assigned infants to one of three conditions.
All infants heard infant-directed speech; what varied was the experimenter's comments during
familiarization. See Figure 1.
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Insert Figure 1 here
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We reasoned as follows: If infants detect the presence of the novel word, and if novel words
direct infants' attention to object categories, then infants who hear novel words during familiarization
should be more likely than those in the No Word condition to form object categories. Including both a
Novel Noun and Novel Adjective condition permitted us to test the specificity of infants’ initial
expectation. If the expectation is initially general, as we have proposed, then infants hearing either
novel nouns or adjectives should be more likely than those hearing no novel words to form object
categories.
For infants who had begun to produce words on their own, the data were entirely consistent
with this prediction. Interestingly, the facilitative influence of novel words was most powerful on
superordinate level trials. On basic level trials, all infants successfully formed categories. But on
Early word learning 14 superordinate trials, infants in the No Word condition did not detect the commonalities. This difficulty
is likely due to the fact that there is considerable variation among category members at superordinate
levels, and as a result, the commonalities among them can be difficult to trace. However, infants who
heard novel words during familiarization (either count nouns or adjectives) detected the commonalities
among objects and successfully formed superordinate level object categories.
These results reveal that infants on the threshold of producing language can reliably detect
novel words presented in fluent speech, and that these novel words (both adjectives and nouns) direct
infants' attention to commonalities among objects. We have interpreted this finding as evidence that
words serve as “invitations to form categories” and have pointed out that this invitation has several
consequences. First, novel words invite infants to assemble together objects that might otherwise be
perceived as disparate entities. We suggest that words promote comparison among objects, and that
this process of comparison supports the discovery of other commonalities that might otherwise have
gone unnoticed (Booth, 2006; Chambers, Graham, & Turner, 2008; Gelman, 2006; Gentner & Namy,
1999; Keates & Graham, 2008; Welder & Graham, 2006).
Naming may also have dramatic consequences in situations in which infants have already
formed groupings and noticed (some of) the commonalities among objects. For example, although
infants in this series successfully formed basic level object categories (whether or not they were
introduced to novel words), their knowledge about these categories is not on a par with the knowledge
of an older child or adult. Even preschool-aged children lack detailed knowledge about most categories
(Gelman, 1996; Keil, 1994). Nonetheless, despite their relative lack of information, children seem to
expect that members of object categories share deep, non-obvious commonalities. Indeed, children
depend upon these to support inference and induction. We suspect that novel words are instrumental in
motivating infants and young children to discover the deeper commonalities that underlie our richly-
structured object categories (Ahn & Luhmann, 2004; Barsalou, 1983; Barsalou, Santos, Simmons, &
Wilson, 2008; Gelman, 1996; Gelman, Coley, & Gottfried, 1994; Gelman & Kalish, 2006; Gelman &
Early word learning 15 Medin, 1993; Kalish & Gelman, 1992; Keil, 1994; Landau, 1994; Landau, Smith, & Jones, 1988;
Lassaline & Murphy, 1996; Macnamara, 1994; Markman, 1989; Medin & Heit, 1999; Murphy 2004).
Most importantly, the results of this series of experiments document that a link between word-learning
and conceptual organization is in place early enough to guide infants in their very first efforts to
establish word-to-world mappings.
Specifying the scope of infants’ word-to-world mappings. Having shown that words promote
the formation of object categories, our next goal was to capture more precisely the scope, power and
evolution of infants’ expectations in word-learning (Booth & Waxman, 2003; Waxman & Booth,
2001b, 2003). To do so, we extended the work described in the previous section in four ways. First,
we included a developmental component, comparing the performance of 11-month-old infants on the
very threshold of producing words with that of 14-month-olds whose lexicons already include a
modest set of entries. Second, we expanded the range of commonalities under investigation. In the
previously-described studies (Waxman & Markow, 1995), the only commonality among objects was
category-based (e.g., four animals, all of a different color). Here, we ask whether infants link novel
words specifically to category-based commonalities (e.g., animal), or whether they also link words to a
wider range of groupings including, for example, property-based commonalities (e.g., pink things,
lumpy things) (Waxman, 1999).3 Third, we considered the influence not only of nouns, but also of
adjectives, on infants’ categorization behavior.
A fourth goal in this series was methodological. All of the evidence reviewed thus far has been
based entirely on infants’ performance in novelty-preference tasks. In the current series, we asked
whether infants’ expectations would influence performance in a word extension task. Our goal here
was to bridge a methodological gap between research with infants and preschoolers. Novelty-
preference tasks have been successful with infants, but beyond 18 months of age, infants lose interest
in such tasks. Word-extension tasks have been successful with toddlers and preschoolers, but lack
Early word learning 16 sensitivity with infants under 18-months, who have difficulty choosing systematically among objects
in forced-choice tasks.
To bridge this methodological gap, we developed a new method, which weds features of the
novelty-preference procedure with those of the word-extension paradigms. See Figure 2 for a
schematic description of the procedure and a summary of the instructions presented in each condition.
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Insert Figure 2 here
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In the Familiarization phase, an experimenter introduced infants in all conditions to four
objects, all drawn from the same object category (e.g., horses or animals) and embodying the same
object property (e.g., purple). These were presented in pairs, and infants manipulated them freely.
During the Contrast phase, the experimenter presented a new object (e.g., a brown rolling-pin), drawn
from a contrastive object category and embodying a contrastive object property. In the Test phase,
infants were presented with one familiar object (e.g., a purple horse), and one novel object. For half of
the infants in each condition (see below), this novel object was a member of a novel object category,
but embodied the same property (e.g., a purple plate). This constituted a Category test. For the
remaining infants, the novel object was a member of the same category as the familiarization objects,
but embodied a novel property (e.g., a blue horse). This constituted a Property test. Infants were first
permitted to play freely with the two test objects. Then, to assess word-extension, the experimenter
removed the test objects. At this point, she introduced a target object, drawn from the familiarization
set (e.g., a purple horse) and then re-presented the two test objects, asking the infant to give her one.
(See Figure 2). This word-extension task was presented a second time for each set of familiarization
objects. This permitted us to observe the consistency of infants’ responses. Infants completed this
entire procedure four times, with four different sets of objects, two representing basic level object
categories and two representing superordinate level categories.
Early word learning 17 To trace the proposed developmental trajectory from an initially general expectation linking
open class words (either count nouns or adjectives) to commonalities among objects (either category-
based or property-based) to a more specific set of expectations, we compared the influence of novel
nouns and adjectives in the performance of infants at 11 and 14 months of age. If infants begin the
process of lexical acquisition with a broad expectation linking words (in general) to commonalities
among objects (in general), then for 11-month-olds, both nouns and adjectives should highlight both
category-based (e.g., animal) and property-based (e.g., purple things) commonalities. If this initial
expectation is refined once the process of lexical acquisition is under way, then for more advanced
learners, a different pattern should emerge: Different kinds of words should direct older infants’
attention to different aspects of the same experience: naming objects (with either a count noun or
adjective) should systematically influence infants’ construals of the very same set of objects (e.g.,
purple animals) either as members of an object category (animals) or as embodying an object
property (purple). Based on our previous work (Waxman, 1999b; Waxman & Booth, 2000a), we
expected that at 14 months, infants would have begun to distinguish count nouns (from among the
other grammatical forms) and to map these specifically to category-based, but not property-based,
commonalities. We expected that at this same developmental moment, infants’ expectations for
adjectives would still be quite general, directing their attention more broadly toward commonalities (be
they category- or property-based).
The results were consistent with these predictions. At 11 months, infants hearing novel words
(both nouns and adjectives) performed differently than those in the No Word condition. Infants
extended both novel nouns and adjectives consistently to the familiar test object (e.g., the purple horse)
on both Category and Property trials. This confirms that at the very onset of building a lexicon, (a)
novel (open class) words direct infants’ attention broadly to both category- and property-based
commonalities among named objects, and (b) this link is sufficiently strong to support the extension of
novel words. This outcome provides strong support for our proposal that infants on the very threshold
Early word learning 18 of word-learning harbor a general expectation linking words (both nouns and adjectives) to
commonalities (both category- and property-based) among objects.
We also proposed that once word-learning is underway, a more specific pattern should emerge.
Evidence from 14-month-olds offers support for this developmental prediction. By 14 months, infants
were sensitive to the distinction between novel words presented as nouns as compared to adjectives,
and they recruited this distinction in mapping words to their meaning. They mapped nouns to category-
based, rather than to property-based, commonalities. However, their expectations regarding the
extension of novel adjectives were more general. Infants hearing adjectives were equally likely to
select the familiar object on both types of test trials (see Waxman, 1999b; Waxman & Booth, 2000a
for replications and extensions using various properties (e.g., color, texture)). Clearly, by 14 months,
infants have begun to distinguish among different kinds of words (nouns vs. adjectives) and recruit this
distinction in the service of mapping words to their meaning.
Additional support for this developmental trajectory comes from a recent study using a
precisely controlled automated method (Booth & Waxman, 2009). This method offers two advantages
over the studies described above, which all involved direct interaction between an infant and
experimenter: 1) it allows for tight control over the presentation of stimuli, and 2) it permits us to trace
the time course of children’s mapping of novel words to meaning (Fernald, Swingley, & Pinto, 2001;
Fernald, Pinto, Swingley, Weinberg, & McRoberts, 1998; Golinkoff, Hirsh-Pasek, Cauley, & Gordon,
1987; Swingley, Pinto, & Fernald, 1999). In this study, 14- and 18-month-olds watched a video that
mirrored the structure of the earlier studies. Their response was measured by examining the infants’
eye movements during the test period. Examining which of two images the infant paid more attention
to during this period provided an indirect measure of how they extended the novel noun or adjective.
Once again, infants at both ages in this study extended novel nouns to other members of the
same category, as opposed to items sharing the same property. Moreover, the time-course of their
extension was swift, occurring within two seconds of hearing the novel word. When the same words
Early word learning 19 were presented as adjectives, infants revealed no preference for either category- or property-based
extensions. This finding lines up with the results of previous studies, which suggest the adjective-
property link may begin to emerge just after 18 months, or during the 18- to 21-month time frame
(Waxman & Markow, 1998).
The convergence between performance in this automated procedure and in the live tasks is
striking. Taken together, they show that clearly, 14-month-olds are sensitive to (at least some of) the
relevant cues (e.g., prosody, morphology, structural position within a phrase) that distinguish count
nouns from adjectives. Cues like these are sufficiently rich to support an emerging distinction among
major grammatical forms (Morgan & Demuth, 1996). Although infants’ grammatical distinctions are
certainly not as well-honed as those of adults, and although their knowledge of categories and
properties of objects is certainly not as rich, 14-month-olds do appear to share with adults an
expectation that different types of words (count nouns versus adjectives) refer to different types of
relations among objects.
Talking two-year-olds: beyond nouns and adjectives. Having examined the trajectory of
infants’ mapping of novel nouns and adjectives, we turn our attention now to the acquisition of verbs.
Verbs do not appear in appreciable number in infants’ productive lexicons until several months after
the appearance of nouns (between roughly 20 - 24 months) (For recent reviews, see Gleitman, Cassidy,
Nappa, Papafragou and Trueswell, 2005; Waxman and Lidz, 2006). This developmental phenomenon,
favoring the acquisition of nouns over verbs, suggests that these distinct grammatical forms differ not
only in the kinds of meanings they convey, but also in their underlying course of acquisition. In the
next series, we look at what it takes to learn a verb.
The conceptual underpinnings of verbs seem to be in place, at least in rudimentary ways, by the
end of the first year of life. By 8 – 12 months, infants are sensitive to certain fundamental components
of events, including animacy, agency, and cause (Buresh, Wilson-Brune & Woodward, 2006; Casasola
& Cohen, 2000; Gergely & Csibra, 2003; Gergely, Nádasdy, Csibra, & Bíró,1995; Gertner, Fisher, &
Early word learning 20 Eisengart, 2006; Golinkoff & Hirsch-Pasek, 2006; Leslie & Keeble, 1987; Meltzoff, 2007; Muentener
& Carey, 2006; Sommerville, Woodward, & Needham 2005; Wagner & Carey, 2005). Between 12 and
24 months, infants demonstrate sensitivity to other key elements of events, including changes of state,
result, manner and path of motion (Bunger, 2007; Bunger & Lidz, 2004; Pruden, Hirsh-Pasek,
Maguire, & Meyer, 2004; Pulverman, Hirsh-Pasek, Pruden, & Golinkoff, 2006).
What this means is that infants’ relatively delayed acquisition of verbs must not be due to an
inability to represent the kinds of concepts that underlie verb meaning, but rather to other factors.
What might these factors be?
One possibility is that infants’ relative delay in acquiring verbs reflects the fact that the
meaning of a verb depends upon the arguments that it takes (and the relation among them). Simply put,
to identify the event labeled by a verb, learners depend upon the noun phrases that represent the event
participants and the linguistic relations among these phrases (Fisher, Hall, Rakowitz, & Gleitman,
1994; Gillette, Gleitman, Gleitman & Lederer, 1999; Gleitman, et al., 2005; Landau & Gleitman, 1985;
Lidz, Gleitman & Gleitman, 2003; Piccin & Waxman, 2007; Snedeker & Gleitman, 2004; Waxman &
Lidz, 2006). Therefore, without the nouns, it should be difficult for learners to identify the arguments
of a verb and impossible to identify the event labeled by the verb in that context. The acquisition of
verbs must therefore follow the acquisition of nouns.
This trajectory is supported by studies of toddlers’ vocabularies. Productive use of verbs to
refer to actions, mental states, and relations is often not established until 24 months, well after the
productive use of nouns (Fenson, Bates, Dale, Goodman, Reznick, & Thal, 2000). Around this age,
not only do toddlers produce verbs, but they seem to map novel verbs onto categories of events, taking
into account syntactic information, including the number and types of frames in which novel verbs
appear and the relations among the noun phrases in these frames, to narrow their hypotheses about
possible verb meanings (Akhtar & Tomasello, 1996; Bunger & Lidz, 2004; Fernandes, Marcus,
DiNubila, & Vouloumanos, 2006; Fisher, 2002; Gertner, Fisher, & Eisengart, 2006; Gleitman, 1990;
Early word learning 21 Gleitman et al., 2005; Hirsch-Pasek, Golinkoff, & Naigles, 1996; Landau & Gleitman, 1985; Naigles,
1990, 1996; Naigles & Kako, 1993).
Nonetheless, the verb learning literature also reveals some astonishing failures, many of which
persist throughout the preschool years (Imai, Haryu, & Okada, 2005; Imai, et al., 2008; see also
Behrend, 1990; Kersten & Smith, 2002; Meyer et al., 2003). A review of the evidence suggests that
infants and young children succeed in verb-learning when the very same participant objects are present
in all the events, but encounter difficulty when there is a change in the event participants. This
suggests that infants and even young children are essentially “captured” by the participant objects and
have difficulty extending verbs beyond them.
Interestingly, infants appear to be captured by participant objects in laboratory tasks, but not in
real-world acquisition. Children are often observed extending verbs like “drink” to different beverages
(e.g., milk, water), “run” to different actors (e.g., dogs, people), etc. outside of the laboratory. How
can we account for this mismatch? What information is missing from laboratory tasks that hampers
children’s ability to learn novel verbs?
We examined infant verb-learning using the automated procedure described above (Waxman,
Lidz, Braun, & Lavin, 2009). Videos of dynamic scenes (e.g., a man waving a balloon) were presented
to 24-month-old infants. The study examined whether infants could construe these scenes flexibly,
noticing the consistent action (e.g., waving) as well as the consistent object (e.g., the balloon) and b)
whether their construals of the scenes were influenced by the grammatical form of a novel word used
to describe them (verb or noun). Infants were presented with the scenes in a Familiarization phase,
where the accompanying audio varied as function of condition. Afterward, during the Test phase,
infants saw two test scenes, presented simultaneously on either side of the screen. Both scenes featured
the same actor (e.g., the man) and the same object (e.g., the balloon) as in familiarization; what varied
was the event in which these two were involved. In the familiar test scene, the man performed the now-
Early word learning 22 familiar action (e.g., man waving a balloon); in the novel test scene, he performed a novel action (e.g.,
man tapping a balloon). See Figure 3 for the audio presented in each phase of each condition.
Infants’ visual attention during each frame of the Test phase was analyzed, measuring attention
to the novel event (e.g. a man tapping a balloon) versus the familiar event (e.g. a man waving a
balloon). These time-course results revealed that infants were sensitive to the consistent events shown
during familiarization, as they exhibited a strong novelty preference (directing their attention to the
novel event) before hearing the test sentence that varied by condition. Once the infants heard the test
sentence (e.g., “Where’s larping?), their attention began to diverge. Children in the Verb condition
reliably directed their attention back toward the familiar event, or the event labeled with the novel verb
during familiarization (e.g. waving a balloon). Children in the Noun and No Word conditions
maintained their visual attention on the novel event. Note that both the novel and familiar events
included a balloon, making them both appropriate responses for the Noun condition. However, a
subsequent experiment using the same Familiarizaton phase, but changing the Test phase to include
events with the same action but different objects (e.g., waving a balloon versus waving a rake)
revealed that children could indeed appropriately extend a novel noun and direct their attention back to
the familiar object.
These results suggest that 24-month-olds’ representations of novel words are sufficiently
precise to permit them to map novel verbs to event categories (e.g., waving events) and novel nouns to
object categories (e.g., balloons). Once again the time-course of their mapping is swift, occurring
within about a second of hearing the novel word. These results beckon us to move beyond asking
whether or not infants can represent verb meanings, and to consider instead the conditions that support
their successful acquisition.
Avenues for future research
Early word learning 23 The evidence discussed above has significantly advanced our understanding of children’s early
word learning, while simultaneously prompting myriad avenues for future research. Among them are
questions concerning how word learning proceeds in bilingual children, and what neuropsychological
studies can contribute to theories of word learning. We consider each of these in turn below.
Word-learning in bilingual environments. The previous sections highlight the many challenges word-
learning presents to infants and young children. The task for bilingual children is even more complex, as
they grapple with solving the puzzle of word-learning in more than one language. Nevertheless, the time-
course of bilingual children’s acquisition is similar to that of monolinguals (Holowka, Brosseau-Lapre, &
Petitto, 2002; Oller, Eilers, Urbano, & Cobo-Lewis, 1997; Pearson, Fernandez, & Oller, 1993), and their
early words and sentences closely resemble those of monolingual infants (Yip & Matthews, 2007).
Monolingual and bilingual word learning nonetheless differs in important ways (see Fernald,
2006; Werker & Byers-Heinlein, 2008 for recent reviews). Bilingual infants must separate the
linguistic input that they receive from their two languages, forming two distinct phonological systems
and two lexicons. An active area of research is the way the two languages might be represented and
processed in the brain. A recent neuropsychological study examined brain responses in 19- and 22-
month-old bilingual infants as they listened to known and unknown words in both of their languages
(Conboy & Mills, 2006). Differences were found not only the infant brain responses to known and
unknown words, but also in the infant brain responses to the two languages. Moreover, the timing and
distribution of brain activity linked to word-meaning differed for children’s dominant vs. non-
dominant language. These differences most likely reflect differences in the infants’ experience with
the two languages, rather than a general brain maturational mechanism.
The neuroscience of word-learning. Other recent neuropsychological studies contribute to our
understanding of the neural processes underlying word-learning in both bilingual and monolingual
environments, and support the behavioral findings detailed above in two main ways. First,
neuropsychological evidence shows that the infant brain responds to speech in a special way, distinct
Early word learning 24 from other auditory signals. This dovetails well with evidence that infants map words (but not non-
speech stimuli like tones) to meaning (Fulkerson & Waxman, 2007). Second, there is evidence that the
infant brain responds in a specific way not only to speech sounds in general, but also to words in
particular. This specific response to the presentation of words provides the first neurological correlates
of word learning.
The evidence that even newborn infants process speech stimuli in a way that is distinct from
non-speech stimuli suggests that the human brain comes prepared to process human speech. In
particular, areas of activation observed in the newborn brain bear a striking resemblance to those for
adults. Two recent studies examined areas of brain activation in neonates (Pena, et al, 2003) and 3-
month-olds (Dehaene-Lambertz et al, 2002). These studies revealed that even in neonates there is a left
hemisphere bias when listening to language, a bias that is not observed when listening to backwards
speech or silence. Moreover, this left hemisphere bias was shown to emerge even when subjects were
presented with a language other than their own (Hespos, Ferry, Cannistraci, Gore, & Park, 2009;
Hespos, Park, Ferry, Lane, & Gore, 2009).
Recent work also shows that infants go beyond merely processing speech sounds in speech-
specific ways, but that they can also detect speech patterns, like the repetition of syllables (Gervain, et
al, 2008). Different patterns of brain responses emerged when neonates were presented with blocks of
syllables with immediate repetition (e.g., ABB) vs. no repetition. This indicates that the infant brain is
sensitive to speech structure, and suggests at least one way in which neuropsychological capacities
support the acquisition of words.
Beyond speech processing, neurospsychological research on word-learning primarily consists
of ERP studies that use the N400 as a method of testing children’s knowledge. The N400 is an ERP
response that is associated, in adults, with semantic integration. It is consistently observed after an
unexpected stimulus, as when a picture is paired with a mismatching names (e.g., pairing the word
Early word learning 25 “dog” with a picture of a banana). (See Werker & Yeung, 2005 for a terrific overview of ERP
correlates to word learning)
The N400 response has been observed in several studies of infants and toddlers. In one study,
19-month-olds were presented with known words that either matched or did not match a sequentially
presented picture (Friedrich & Friederici, 2004). The words referred to the basic level name of the
object or an incongruent basic level name. As expected, the N400 emerged when the object names did
not match the object pictures. A later study obtained this same result with 14-month-olds (Friedrich &
Friederici, 2005). Studies featuring novel words have also revealed the N400 in infants and young
children (Mills, Plunkett, Prat, & Schafer 2005; von Koss Torkildsen et al., 2008).
In conclusion, the neuropsychological evidence converges well with the behavioral evidence on
word-learning. Recall that behavioral studies reveal that by 14 months, infants have mapped several
nouns to objects and object kinds. Correspondingly, neuropsychological studies show that when a
mismatch occurs between a known noun and picture of an object, the 14-month-old infant brain
‘notices’ the mismatch. As research in this field progresses, it will be interesting to see if
neuropsychological correlates are also evident in the infant brain’s response to words from other
grammatical categories, including adjectives and verbs.
Conclusions
In this chapter, we have focused on word-learning, asking what expectations, if any, infants
recruit in the process of establishing their first word-to-world mappings, and how these evolve over
development. We suggested that infants begin the task of word-learning equipped with a broad, initial,
and universally-available expectation that links novel open class words (independent of their
grammatical form) to a wide range of commonalities among named objects. We suggested that this
initially general expectation sets the stage for the evolution of more specific expectations, calibrated in
Early word learning 26 accordance with the correlations between particular grammatical forms and their associated meanings
in the language under acquisition.
Infants’ performance provided clear support for this proposal. At 11 months, infants revealed a
broad initial expectation, linking words (count nouns and adjectives) to commonalities (both category-
and property-based) among named objects. By 14 months, infants’ expectations have indeed become
more fine-tuned. They distinguish nouns from adjectives, and treat this distinction as relevant when
mapping words to their meaning (mapping count nouns specifically to category-based, but not
property-based, commonalities among objects). Specific links between adjectives and properties of
objects continue to emerge toward the end of the second year of life. By this age, infants also begin to
map verbs to commonalities among events as well.
These results point to substantial continuity across development in the types of concepts we
form, and in the influence of naming in their acquisition. We see this line of work as providing
evidence that words are powerful engines for conceptual development: words advance us beyond our
initial groupings, fueling the acquisition of the rich relations that characterize our most powerful
concepts.
Finally, this developmental account has several distinct strengths. First, it embraces both the
importance of the expectations imposed by the learner, as well as the shaping role of the environment.
In the case of word-learning, this interplay between factors inherent in the child and factors within the
environment is essential. Infants across the world will encounter different objects, will acquire
different languages, and will be provided with different types of language input (Cole, Gay, Glick, &
Sharp, 1971; Laboratory of Comparitive Human Cognition, 1983).
Moreover, under our proposal, early acquisition is sufficiently constrained to permit infants to
form fundamental categories of objects and to learn the words to express them, and sufficiently flexible
to accommodate the systematic variations in the word-to-world mappings that occur across languages.
Notice that our view of constraints on acquisition is not an argument based entirely on assumptions of
Early word learning 27 innate knowledge. Neither is it a polarized argument that locates the engine of acquisition solely within
the mind of the child. Rather, the idea is that in the process of word learning, infants direct their
attention toward precisely the sort of information and precisely the kinds of regularities in the
environment that will support foundational concepts and the acquisition of words to describe them.
Our proposal is flexible enough to account for the fact that infants naturally acquire a wide range of
human languages, and that these differ in the ways in which they recruit the particular grammatical
forms to convey particular types of meaning. We have suggested that the specific links between
particular grammatical forms and their associated meanings are calibrated on the basis of correlations
or regularities that are present in the language under acquisition. It therefore stands to reason that these
more specific links would not be available at the onset of word-learning, but instead would emerge
later, once the process of lexical acquisition is underway.
Finally, our proposal is a dynamic one: The initial expectations that we observe in infants at the
outset of acquisition are not rigidly fixed, exerting a uniform influence throughout development. On
the contrary, these expectations are shaped over the course of development in accordance with the
observed regularities in the language under acquisition.
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Early word learning 40
Figures
Figure 1. A schematic presentation of introductory phrases from Waxman & Markow (1995) and an example of a single stimulus set
_________________________________________________________________________________________________________ Familiarization Phase Test Phase Trial 1 Trial 2 Trial 3 Trial 4 Animal Set: yellow duck green raccoon blue dog orange lion red cat red apple ________________________________________________________________________ __________________ Noun This one is. This one is See what I have? This one is See what I have? a(n) X a(n) X a(n)X Adjective This one is This one is See what I have? This one is See what I have? X-ish X-ish X-ish No Word Look at this. Look at this. See what I have? Look at this. See what I have? _________________________________________________________________________________________________________
Early word learning 41
Figure 2. A schematic presentation of introductory phrases from Waxman & Booth (2001) and an example of a single stimulus set
Familiarization Contrast Test
Trial 1 Trial 2 Category Property
Purple Animal Set:
bear lion
elephant dog
red apple
purple horse vs. purple chair
purple horse vs. blue horse
Noun
These are blickets.
This one is a blicket & This one is a blicket
These are blickets.
This one is a blicket & This one is a blicket
Uh-oh, this one is not a
blicket!
Can you give me the blicket? Can you give me the blicket?
Adjective
These are blickish.
This one is blickish & This one is a blickish
These are blickish.
This one is blickish & This one is a blickish
Uh-oh, this one is not blickish!
Can you give me the blickish one?
Can you give me the blickish one?
No Word
Look at these.
Look at this one & Look at this one
Look at these.
Look at this one & Look at this one
Uh-oh, look at this one!
Can you give one? Can you give me one?
Early word learning 42
Figure 3. A schematic presentation of introductory phrases from Waxman, Lidz, Braun, & Lavin (in press) and example of a single stimulus set.
Early word learning 43
1 From Keller (1904). 2 Note, that this was, in fact, Keller’s second language. She had begun to acquire English before becoming deaf and blind. 3 This question itself hinges on there being a psychological distinction between object categories and object properties. Recent
approaches in cognitive psychology distinguish object categories (sometimes known as kinds or sortals) from other types of groupings (e.g.,
pink things, things to pull from a burning house) on at least 3 (related) grounds: Object categories (1) are richly-structured, (2) capture many
commonalities, including deep, non-obvious relations among properties (as opposed to isolated properties), and (3) serve as the basis for
induction (Barsalou, 1983; Gelman & Medin, 1993; Kalish & Gelman, 1992; Macnamara, 1994)(Medin & Heit, in press)(Murphy & Medin,
1985). Although infants and children lack detailed knowledge about most object categories, they clearly expect named object categories to
serve these functions (Gelman, 1996; Keil, 1994). In addition, there is now evidence for a psychological distinction between individual
properties and relations among properties in infancy (Bhatt & Rovee-Collier, 1997; Younger & Cohen, 1986). We selected color and texture
because these properties are perceptually salient to infants, and because these property-based commonalities typically do not underlie object
categories. We suspect that an object’s shape is more centrally related to category membership, particularly for simple artifacts and for animate
objects (Waxman & Braig, 1996).